The basic manufacturing method of China’s six major teas is to select and combine the following processes to form different teas.
Green tea: fresh leaves -> fixing -> Shaping -> drying
Chinese Red tea [Black tea]: fresh leaves -> withering -> Shaping -> oxidising -> drying.
Oolong tea: fresh leaves -> withering -> bruising -> fixing -> Shaping -> drying
White tea: fresh leaves -> withering -> drying
Chinese Black tea [Dark tea]: fresh leaves -> fixing -> Shaping -> piling -> drying (the raw Pu’er does not have a piling process)
Yellow tea: fresh leaves -> fixing -> Shaping -> muffling -> drying
1. Fixing or “De-enzyming” / “Killing the green”
Fixing is very important to tea. High temperature is used for curing to quickly destroy the activity, prevent polyphenols from being oxidized, and at the same time increase the aroma of tea, lay the foundation for the taste of tea soup, continue to volatilize the fresh leaf moisture, and the leaves become soft, which is convenient for subsequent twisting. For green tea, there are two ways to make it: stir-fried and steamed. China’s existing tea is mainly roasted green, such as Dragon Well tea and Taiping Houkui. Japan retains the traditional steaming technique and applies it to most of the existing Japanese teas, such as matcha and sencha. Finishing is also the basis for forming the quality characteristics of yellow tea and dark tea. The curing temperature of raw Pu’er is low, and the oxidase of tea is not completely passivated. As time goes by, the oxidase will recover and catalyze the oxidation degree of tea in the later stage, forming a unique aging taste.
Withering can enhance enzyme activity for tea that needs to be Oxidised. Promote the volatilization of water from tea leaves and thus removing the grassy notes, preparing for subsequent processes. Withering is divided into sunlight withering, indoor natural withering and heating withering. Chinese Red tea [Black tea] is mostly used indoor natural withering method. Sunlight withering has higher requirements for natural environmental weather conditions, and is mostly used for oolong tea. The degree of sun-greening also varies with tea, and it is usually heavier in northern Fujian than in southern Fujian. As the only step before white tea is dried, white tea has a much greater degree of withering than black tea. The long duration also means more variables, and very high requirements for specific weather conditions.
The purpose of shaping is to shape the tea under the action of external force, increase the concentration of the tea soup, and improve the internal quality of the tea. The black tea crushes the mesophyll cells and prepares for Oxidation. Different types of tea require different degrees of kneading, such as variants with pekoes, which requires more gentle kneading. The crushed black tea is cut while kneading during the kneading step.
Chinese red tea [Black tea] is fully oxidised, while green tea is not oxidised, oolong tea is semi-oxidised, and white tea is naturally oxidised. This is an important step to form the flavor and quality of the oxidised tea. The chemical change of oxidation starts from rolling until the end of drying. The essence of Chinese red tea fermentation is to enhance the activity of enzymes and promote the oxidative polymerization of polyphenols to form the aroma of the tea. Souchong black tea has added a smoking step to make the tea leaves have a pinewood fragrance.
5. Bruising / Disruption
According to the different seasons, tea varieties, regions, and the degree of bruising time varies. Some of the methodologies include the cooling method, the shaking method, and the piling method. It is an important process that affects the quality of oolong tea. Tea oxidation is relatively heavy in northern Fujian, while Oolong oxidation in southern Fujian and Taiwan is relatively light. The Guangdong Oolong Craft is close to the Oolong in Northern Fujian. Through the collision and friction between the leaves, the leaf margin cells are destroyed and oxidized, forming a special quality of “red trim”, the soup is golden in color, and the fragrance is rich. Water will diffuse from the stems and buds with higher water content to the leaf surface with low water content (water removal), producing a lot of aromatic compounds.
6. Muffling / Yellowing
After fixing, a chemical reaction occurs in the leaves under the action of heat and humidity. The time is shorter than that of black tea, and the content of the leaves changes less, resulting in yellowish or yellowish brown leaves. The representative Junshan Silver Needle, using fat and tender bud tips, has a golden and bright color and a sweet and refreshing taste. Different yellow teas have slightly different yellowing time processes.
The kneaded tea leaves are piled up, and part of the astringency and rough taste are removed through the heat and humidity in the pile. It is a post-oxidation process. There is an active microbial reaction. A large amount of cellulose and pectin in crude tea leaves are degraded by microorganisms, making the leaf stems soft and forming the unique flavor of Chinese black tea [dark tea].
The purpose of drying is to evaporate water, make tea easy to store by halting the enzyme activity of oxidised leaves, and stop oxidation to fix the quality. Fixing the tea’s color, fragrance and taste. Drying is often combined with further styling. In the process of evaporating water, the phosgene produced by the tea is transformed and volatilized, and aromatic substances are generated, such as the floral and fruity fragrance of dry tea, and the sweetness, while increasing the sweetness and layering of the tea soup.
9. Rolling and roasting
Rolling is a unique process that promotes the formation of curls or the spherical shape outside of oolong tea. Among them are the manual kneading method and machine kneading method. Roasting is the final process of some oolong tea, including initial roasting and re-roasting. There is no rolling process for Oolong in Northern Fujian.